Cranes generally utilize a counterweight to generate a moment which counters the working load and thus ensures the stability of the crane. If the counterweight is fixedly connected to the crane, only one defined counterweight moment can always be applied. If the crane is to take up more or less load, the counterweight moment can only be adapted to the current load by stacking up or taking away counterweight plates.
Various deliberations have already been made to remedy this disadvantage. One of these deliberations had the result that the weight of the counterweight is left constant and the effective spacing of the counterweight, that is the counterweight radius, is adapted.
A corresponding crane having a counterweight arrangement which can be telescoped out is thus known from EP 0 989 087 A1.
In '087, a counterweight arrangement is already connected to the superstructure of a derrick crane by a telescopic carrier. The telescopic carrier can be telescoped out or pushed out in accordance with the respective load case or in accordance with the respective luffing angle of the boom so that the counter torque corresponding to the pivot angle of the boom can be generated in a simple manner by a corresponding telescoping out of the counterweight arrangement.
A derrick crane is likewise known from EP 1 135 322 B1 in which a counterweight arrangement is telescopically supported. Therein, the counterweight arrangement is continuously variable in a defined region via a frame element, with the frame element being arranged movable in the vertical plane at the superstructure. The axially fixed frame element is furthermore connected to the superstructure via a vertically acting piston-in-cylinder unit to displace the resulting force between the counterweight force acting in the direction of gravity and the guying force generated by a suspended load into the superstructure as required.
A crane which can also be used as a derrick crane as required is also known from EP 2 281 771 A1 in which the counterweight arrangement can be telescoped out.
In the known cranes having a counterweight arrangement which can be telescoped out, the counterweight arrangement is only displaceable over a limited lengthways region due to the design. In this respect, the counterweight arrangement can typically only be traveled behind the superstructure platform along corresponding carriers which may optionally be able to be telescoped out.
It is the object of the present disclosure to increase the adjustment range for the counterweight arrangement.
This object is achieved in accordance with a crane, such as a derrick crane, which has a travelable undercarriage and a superstructure which is rotatably supported thereon, at which a boom is luffably connected in an articulated manner, on the one hand, and at which a counterweight arrangement is telescopically supported, on the other hand, the crane equipped with a counterweight arrangement comprising a U-shaped frame in which a likewise U-shaped counterweight frame is telescopically guided. The frame and the counterweight frame may each substantially comprise two side members and one cross-member. The counterweight plates forming the counterweight are separated into two stacks which are each longitudinally displaceably guided independent of one another on a side member.
The region in which the counterweight arrangement is displaceable relative to the axis of rotation, that is the axis of rotation of the superstructure about the undercarriage, is substantially increased by the arrangement in accordance with the present disclosure. In accordance with the present disclosure, the counterweight plates which are here arranged longitudinally displaceably at the respective side of the side members can namely be displaced up to be close to the axis of rotation. This has the effect, on the one hand, that a tilting backward of the crane can also be avoided with small load radii. The center of gravity of the total counterweight arrangement can be displaced within the tilting edges of the crawler crane or can be displaced into the quadrangle of the crawler crane formed by the tilting edges by the displaceability of the counterweight plates close to the axis of rotation in accordance with the present disclosure. This advantageously takes place without any complex restacking of the individual counterweight plates such as would be necessary in the solutions in accordance with the prior art. The ballast torque can be adjusted by the wide-ranging displaceability of the counterweight arrangement such that the load torque is always larger than the ballast torque. The guying hereby always has a positive force.
In one example, the U-shaped frame can be connected to the superstructure in an articulated manner pivotable about a luffing axis.
In another example, the counterweight plates forming the counterweight can advantageously be displaceable via trolleys travelable over the side members of the counterweight frame. In this respect, the side members of the counterweight frame and the trolleys displaceably arranged thereon are built symmetric to one another.
In another example, the counterweight plates can be displaceable from a position close to the axis of rotation of the superstructure about the undercarriage via the corresponding trolleys into an end position at the outer ends of the side members of the counterweight frame before the counterweight frame is telescoped out of the frame together with the counterweight plates as required. In accordance with this example embodiment, on the pushing out of the counterweight, that is of the ballast, the ballast can always first be displaced completely up to the end position on the outer frame before the counterweight frame is pushed out. On the traveling inward of the ballast, the counterweight frame is first completely moved in before the ballast is displaced on the frame.
The position of the ballast can be monitored via corresponding length sensors. In this respect, the deployment states of the ballast on the respective side, that is to the left and to the right of the articulation point of the U-shaped frame at the superstructure up to the center of the counterweight plates, can be measured. The deployment state of the counterweight frame can also be measured at the left and at the right and thus also in a redundant manner.
The crane advantageously has a derrick boom which is pivotably connected to the superstructure in an articulated manner and from whose one end a preferably length-variable guying is connected to the counterweight frame.
In one example, the U-shaped frame of the counterweight arrangement pivotably connected to the superstructure in an articulated manner can particularly advantageously be connected to the superstructure also via a vertically acting displacement means. In one example embodiment in accordance with the present disclosure, the revolving deck ballast typically provided on the superstructure can be omitted. In accordance with the aforesaid example embodiment, the force is generated by the counterweight frame pivotably connected to the superstructure in an articulated manner to replace the force which the revolving deck ballast typically generates on the revolving deck. For this purpose, the counterweight frame is connected to the superstructure via the vertically acting displacement means. This principle of this approach is known from EP 1 135 322 B1.
In accordance with a further example embodiment of the present disclosure, a support device may be arranged at the counterweight frame. The support device ensures that, in the event of a breaking away of the load and thus a backward tilting of the crane, the counterweight arrangement can be quickly supported at the ground so that a further tilting is prevented. The vertical adjustability of the support device advantageously serves to compensate different levels or profiles of the ground.
A cross-frame which is inwardly movable into a support apparatus arranged at the superstructure may be arranged at the counterweight frame. The counterweight frame may be supported at the superstructure via the cross-frame which can be moved inwardly into the support apparatus. The support apparatus can therefore downwardly limit the degree of freedom of the frame about its luffing axis. In this case, the weight of the counterweight arrangement is directly supported by the superstructure if no derrick boom is used.
In a further embodiment of the present disclosure, the trolleys can be movable on the side members of the counterweight frame via hydraulic cylinders. In the same way, the U-shaped frame and the U-shaped counterweight frame can be mutually telescopable via hydraulic cylinders.
Further features, details and advantages of the present disclosure will be explained with reference to an embodiment shown in the figures.